Automatic control of electric arc welding is well known. Generally, such systems include a carriage and track arrangement for moving a welding torch along a weld path and simultaneously supplying the welding torch with low frequency pulsed current. The carriage speed can be adjusted to a desired value and the level of the weld current can similarly be adjusted depending upon the materials involved to be welded.
In the case of pipe welding, the track structure supporting the carriage is generally circular so that the carriage can crawl around the track in a circumferential direction to cause the torch to follow a circular weld path.
In most of the above types of welding operations, the torch is mounted to the carriage for back and forth movement across the weld path as the carriage progresses in a direction parallel to the weld path. This action assures that all areas of the weld path will be heated to provide a fairly reliable weld seam. In present day automatic welding equipment, the back and forth motion is normally effected by a cam arrangement on the carriage and generally follows a sinusoidal pattern. In this respect, a wire feed system for providing filler is mounted on the same torch frame support so that the wire feeding will follow the motion of the torch.
An example of a track and carriage structure particularly suitable for pipe welding is shown and described in our copending Pat. application, Ser. No. 414,286 filed Nov. 9, 1973.